Concat error in PL/pgsql
I don't have a bug template at hand.
Within a plpgsql function, concatenating TEXT strings from tables that allow NULL values return nil results. Please run the following. The result of the second select is nil.
Cheers, H.P.
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create table tconcattest (id char(3),str text);
insert into tconcattest values('hpw',text('Something...'));
insert into tconcattest values('wuh',text('and more of something.'));
create function fconcattest () returns text as'
declare
r record;
output text;
begin
output := text('''');
for r in select * from tconcattest loop
output := output || r.str;
end loop;
return output;
end;
' language 'plpgsql';
select fconcattest();
insert into tconcattest values('abc',NULL);
select fconcattest();
update tconcattest set str='...again' where id='abc';
select fconcattest();
Hans Peter Wuermli <wurmli@freesurf.ch> writes:
Within a plpgsql function, concatenating TEXT strings from tables that
allow NULL values return nil results.
That's not a bug: NULL concatenated with anything produces NULL,
per SQL92 specification.
If you want a NULL to act like an empty string, try
for r in select * from tconcattest loop
output := output || coalesce(r.str, '''');
regards, tom lane
Simple add lines as shown:
for r in select * from tconcattest loop
IF r.str IS NOT NULL THEN
output := output || r.str;
END IF;
end loop;
- Andrew
A few hours ago, I wrote:
Simple add lines as shown:
for r in select * from tconcattest loop
IF r.str IS NOT NULL THEN
output := output || r.str;
END IF;
end loop;
This would probably be better:
for r in select * from tconcattest where str is not null loop
output := output || r.str;
end loop;